Process fob the recovery of glyc



Oct. 27, 1942. A WALMESLEY Re.. 22,213

' PROCESS FOR THE RECOVERY OF GLYCEROL FROM STILL RESIDUES FROMFERMENTATION PROCESSES I Original Filed March 4,. 1939 2 Sheets-Sheet l8 v m A. v

Aniline An ine Aniline; nilin X dlstllled dehydmtlon M sepnr'atlmcarrying water l .jn Anillne Arillne & waten ll 9 A 5 Pu-lfied i vaniline Glycerol crud, Aniline &.Wdiel i distilled gm distilled on i I It I AqUCOl-IS REFINED GLYCERlhE I qwcerd 9'"'" 3 Aniline some mlllne &water I 5 Aniline carrying 2 I 2 extmct'jon Crude liquor l? extractionof crude liquor extracted with fifi or glycerjol with miline Crude anlno aniline from aniline a, i-emfi n't fiycu L 4 Exhaustad crude CRUDELIQUOR mgcarrying aniline q v q fi. Wilt! some mlllne 4 ol glycerol.blzean m1. Steqninq Water carrying aniline 7 residues from aniline.'Wa:l:e

FIG. I.

R. A. WALMESLEY Oct. 27, 1942.

Reissued Oct. 27, 1942 EROL FROM STILL RESIDUES FROM FER- MENTATIONPROCESSES Robert Alan Walmesley, Howwood, Scotland, assignor to ImperialChemical Industries, Limited, a corporation of Great Britain OriginalNo, 2,235,056, dated March 18, 1941, serial No. 259,807. Applicationeforreissue February 21, 1942, Serial. No.

Britain March 4,1938

' '2 Claims; (01. 260-637) The present invention relates to the recoveryof glycerol formed during the fermentation of carbohydrate material; andin particular to the recovery of glycerol present in the still residuesobtained after highly volatile products, e. g. alcohol, acetone andacetaldehyde, have been distilled from the fermented carbohydratmaterial. 7 In the following description and claims, the expressionstill residues is to be read as referring to such material.

As various carbohydrate materials are commonly used in fermentationprocesses, and as the manner of conducting these processe also varieswidely, the crude still residues obtained from the different processescover a wide range of compositions. In all cases, however, the residuescontain a large proportion of non-volatile organic matter, chieflyunfermented and/or unfermentable carbohydrates; and in some casesconsiderable proportions of inorganic substances may also b present.

In addition to th carbohydrate impurities, the residues contain acertain proportion of so-called "acidic" impurities, which appear toconsist mainly of phenolic and fatty acid" derivatives. These acidicimpurities produce'undesirable effectsin glycerol, and in fermentationglycerol they are present in such proportions that no sample offermentation glycerol, however pure otherwise, will pass thespecification tests applied in most countries to dynamite glycerineintended for use in the'manufacture'of explosives. The nature or amountof the organic materials accompanying the glycerol in these stillresidues has hitherto prevented the successful recovery of the glycerolby the distillation methods which ordinarily serve for the purificationof soap-lye or saponiflcation crude glycerines. This is so, even wherethe material sodistilled is not the crude still residue, but theinvolatile portion of an extract thereof in a volatile solventforglycerol, e. g. industrial spirits or methyl alcohol, as

already proposed for this purpose.

This invention has as an object todevise a new method of extractingglycerol from still residues.

A further object is to devise such a method which will be more efficientand economical than previous methods. A still further object is todevise a method of separating glycerol from the materials that accompanyit in still residues which will yield a glycerol which may besuccessfully refined by ordinary distillation processes to a puritysuitable for explosives. Further objects wil1 appear hereinafter. Theseobjects are accomplished by the following invention. r

,431,898. In Great I have found that I can recover the glycerol fromstill residues and from the impurities contained there if I include thestep of extracting the glycerol-containing liquor, under conditions oflow retention of water content, with a solvent v for glycerol consistingessentially of a volatile nitrogen base that is substantially immisciblewith water. I can further conveniently recover the glycerine byextracting the separated glycerinecontaining base with water. a

The basic nitrogenous solvents for glycerol that are suitable for useaccording to my invention'include the primary aromatic amines suchas'aniline and its closely-related derivatives; for example, thetoluidines, and their mixtures with aniline and those heterocyclicnitrogenous bases which are not miscible with water but'are solvents forglycerine such as quinoline. The preferred solvent is aniline; and, ofthe toluidines, the para isomer is preferred to the others on account ofits greater miscibility with glycerol;

The process'of my invention may be applied lther 'directly to a crudestill residue; or to a liquor obtained by a'preliininary extraction ofstill residues with a volatile solvent for glycerol, such as ethyl ormethyl alcohol or with a volatil'e heterocyclic nitrogen base whichismiscible with water, such as pyridine as described in my co-pendingBritish application'8966/38, followed by distillation of the extract torecover the volatile solvent therefrom. I j

In putting my invention into effect, I-may agitate either the suitablyconcentrated still resid'ue or an evaporated extract thereof in" asuitable vessel, preferably at a raisedtemperaturefwith an appropriatequantity of the base. As the presence of any considerable proportion ofwater in the residues-i detrimental to the efilciency of the extractionand to the purity of the extracted glycerol, I prefer to reducethe'water cont'entof the residues, or of the preliminary extract, below30% and preferably below 15% before or during the extraction with thebasic solvent However, reduction of the water content below 5% does notappearto cause further improvement. The process may be applied tosuitably dehydrated residues or extracts at ordinary tempera tu'res;but, although ayery pure product is obtai'nable'in this way, the? yieldis low. 3 I prefer to carry out the extraction ata temperature as' highas the'boili'n'g point of the mixture permits;'

a temperature between 100and 160 gives satisfactory results.-

The quantity of nitrogenous basic-solvent emglycerol present in thecrude liquor; but the advantages of my invention are most strikinglyevident when I use considerably smaller proportions of such a base inwhich glycerol i highly soluble. In such a case, a large proportion ofthe glycerol contained in the residues may b eificiently recovered inthe form of a comparatively strong aqueous solution, e. g. in 20%concentration,

when as little as 10-20 parts'of basic solvent per part of glycerol areused.

When the solvent has been given sufiicient time toextract the glycerolfrom the liquor, the mixture is allowed to settle.

The solution-of glycerol is then separated from the extracted" liquor, W

cooled down to about atmospheric temperatur,e,, and agitated with aproportion of water-sufficient moval of an aqueous distillate. thenpasses to vessel 3, recommencing the cycle.

second extraction with the condensed aqueous distillate from vessel 4.The aqueous phase from vessel 6, containing the small quantity ofglycerol extracted from the aniline phase, is used to extract theincoming aniline solution of glycerol in vessel 2. The exhausted wetaniline passes to vessels 1, in which it is dehydrated, first bymechanical separation of water and then by re- The dried aniline Aftercirculating'several times, the aniline becomes strongly contaminatedwith acidic impurities, and may be-purified by total distillation instill 8. Alternatively, part of the circulating aniline may becontinuously diverted to still 8, puri ,fied,"and returned: tocirculation in vessel 3.

to extract all the glycerol, e. g1, 4 6 times the. 7

amount of glycerol in the extract. Instead of being immediatelyextracted with water, the

glycerol-containing base may be used in a second extraction of crudeliquor, or in a series ofsuch extractions, e..g. ina countercurrentextraction process. a

The aqueous glycerol solution obtained by extractionof the basic solventwith water may be concentrated by distillation, and suitably treated, e.g. by steam-distillation, to remove any solvent that, may be. retainedin it- For some applications of the glycerol solution, such as theproduction of low-freezing fluids, the presenceof traces of the solventis not disadvantageous. The concentratedaqueous extract usually containsabout 3% to 10% of its weight of involatileorganic impurity and. has acopper reductionvalue of about 1% only calculated. as invert sugar. It,may be refined to 98%-99%. concentration with,satis factorily low lossin a single distillation treatment as usually applied to. soap lyeorsaponification crude-glycerines. I r

The solvent separatedfrom the aqueous extract is dried, suitably. bydistillation and recovery of anaqueous, fraction. A number of extractioncycles may be carried outwith thesame quantity of basic solvent beforethe accumulation of acidic impurities in it renderscompleteredistillation necessary.

' The invention is illustrated by the accompanying drawings, in whichFigure 1 is a diagrammatic flow sheet showings two-stage-extractionprocess, and Figure 2 shows a single-stage process. I 1

Referring to Figure ;1, vessels I and 3 form a two-stage countercurrentextraction system. The crude liquor'is fed to vessel Ir, where it is'extracted with aniline that has been: already used in thefinalextraction stage invess'el 3, and from thence the crude passes tovessel 3 in which it is extracted with fresh-aniline. Thisanilineextracts practically all the remainingglycerol in thecrude, and passeswith this glycerol intovessel I. The exhausted crude in 3 is passed towaste through the steam still 4, from'which the aniline which; itcontainsis. distilled ofi and recovered; The aniline phase carryingglycerol in solution passes to vessel: 2, whichwith vessel 6 forms atwo-stage countercurrenaextraction sys- The anilinesolution of;glycerolcoming from vessel'l is cooled, and mixed in, vessel 2 with water thathas been already used for extraction in, vessel 6. "Themixturesettlesinto a lower aniline phase containing alittle water andglycerol, and an upper aqueous phase containing "most otthje. glycerolandv some aniline; Theqaniline phase passes to vessel V6, in which itundergoes a The aqueousphase from vessel 2 passes to vessel 5,,-inwhich-it is concentrated by removal of the aniline and most of the waterpresent. The distillate passes to vessels 1, and the concentrate passesto still 9, in which it is refined by vacuum distillation to give thefinal product.

In Figure 2, the crude liquor is extracted with aniline in vessel l. Theglycerol-bearing aniline phase is passedto vessel 3, and the extractedcrude, which contains small quantities of aniline and glycerol, ispassedto the steam still 2, where it is steamed ,to recover the aniline.The ,exhausted crude, is then passed to waste. The condensate fromvessel 2 is mixed in vessel 3 with-a further quantity of waterand theglycerol-bearing aniline, and the mixture is then-permitted to settleinto two layers.

Theaqueous layer, containing the bulk of the glycerol and some aniline,is passed to still 4, in which the aniline and most of the-water isdistilled off,; and the glycerol thereby concentrated. The concentrateis passed to still 1, in which it is refined by vacuum distillation.

The distillate from vessel 4 and-the wet aniline phase from vessel 3 arepassed to vesse1.5 which, in conjunction with vessel 6, effects adehydration of the aniline in the manner already described Withreference to the process illustrated in Fig; 1. Part of the watery.phase is diverted from vessel 5 and treated for the recovery of theaniline dissolved therein. The wet aniline is passedtostill 6, where thewater and some aniline is distilled off and returned to 'vessel'i, andthe dried aniline is returned to simulation. in vessel I. r

Where a high-boiling water-immiscible heterocyclic base, such asquinoline, is used in the extraction process, the process may be carriedout in similar fashion. I

The iollowing examples, in which the parts mentioned are parts byweight, illustrate the '.use of aniline as the nitrogenous basic solventaccording to the invention.

' Example 1 jacketed vessel'ivessel l),.provided with a ther mometer,internal heating coils, mechanical stir ring means and a condenser. Thetemperature of the mixture is raised to about loo -110 C. The contentsof the vessel'arekept :at this temperature and stirreduntil the rate ofincrease in the glycerol concentration of the aniline extract becomessmall. The liquids are't-henallowed to separate, and the upper layerconstituting the main aniline extract is withdrawn to vessel 2. Thelower layer is subjected in vessel 3 to :a further extraction with afresh quantity of aniline, and, after separation of the weak extractthereby obtained, is steam-distilled in steam still I to recover thevanillne' retained in it. The .main aniline extract is :cooled andtreated in vessel 2 with 4 parts water per part glycerol contained inthe aniline extract; the water being used in the form of the weakaqueous solution obtained ,previously :irom .a :second aqueousextraction of a previous thatch of the aniline extract. During' theextraction of the :amiline extract with the weak aqueous solution, themixture is gently agitated. It is then allowed to settle and the twolayers are separated.

The 'wet aniline layer, 'Whichstill contains some glycerol, is passed tov essel '6, where it gently agitated with a similar proportion of asaturated solution :of aniline in water, suitably including thecondensateirom still 4.

'The mixture in vessel '6 is allowed to settle into two layers, and theaqueous layer containing the residual glycerol is passed hackto vessel 2for use in the first extraction of incoming crude liquor. The wetaniline layer is passed tozseparation and dehydration vessels 1 wherethe water and ani- 'lineare separated. The dried aniline is passed tovessel 3, where it is utilized for a second extraction ofsingly-extracted crude liquor, and is then passed to vessel I where itrecommencesits cycle.

The aqueous glycerol layer from vessel 2 is passed to the concentrator5, where the aniline and most of the water are distilled-oil and passe'dto the vessels 1. The concentrate is passed to still 9 for finalrefining toy vacuum distillation;

The concentration of glycerol in the -main aqueous extract is about andafter concentra'tion to 90% strength or :over the extract may be refinedto 98% to 99% glycerine in a single distillation.

Example 2 The procedure in this example .as given in Example 1, exceptthat the extraction of the crude .l-iquor with .anlline is carried outat 120'- 140 C. The aqueous glycerol obtained by concentration of theaqueous extract contains 91.1%

glycerol, 1.9% ash, and 5.4% of residue not volatile at 160 C. Itscopper reduction value, .calculated as invert sugar does not exceed 1%.It maybe refined to 98-99% glycerol content by a single distillation.A.-redisti-llation .of the refined glycerol gives a product that issuitable .for use, inthe form of its nitric ester, in the manufacture ofexplosives.

Example 3 allowed to settle, and the bottom layer of exhausted cruderesidues, containing about 6 parts of aniline and 4 parts :of glycerolretained in the impurities, is drawn ed to a separate vessel 2 andsteamed to recover the aniline. The-condensateis reutilised later in thprocess. The aniline layer, containing 36 parts glycerol and 6 partsimpurity '(chiefly phenolic and acidic bodies) is then cooled and passedto a vessel 3 in which it is agitated with suificient water to ,form a20% solution of glycerol with the glycerol dissolved in the aniline. Forthis purpose the aniline water condensed from the crude-steaming processmay he used with the necessary proportion .of feed water. When allowedto settle, the mixture separates into an aqueous aniline layer, in whichthe major portion of the phenolic and acidic impurities are retained,and an aqueous layer of 20% glycerol, -'contairri-I-1g about 6% to 7%impurity on the weight of glycerol and about 3% of its total weight ofaniline. The aqueous aniline, which contains about 5% of this weight ofwater, is dried *by partial separation and distillation .in 5 and E; andmay be used for the extraction of several more batches of crude residuesbefore the accumulation of impurities necessitates its cornp'lete"redistil-lation.

The aqueous glycer-ine is concentrated in still "'4 at-ordinarypressure, during which the aniline water distilled ofi is collected andtreated 'for the recovery of the aniline. The concentrate, consisting ofglycerol with about 20% involatile impurity, .is then refined by .avacuum distillation, in still I, to 98% to 99% concentration. Therefined glycerol so obtained, when once redistilled, is suitable for usein the manufacture of explosives.

The following tables show the results of analysis .of the input andoutput of each vessel during a run, each table having the same number asis given to the apparatus to which it refers in Figure The heading Tarrefers to the collected inorganic and organic involatile impurities inthe crude liquor.

535: Tar I Water Total 1. Crude extraction 1 Urudestilbresidues. '80 100l '20 200 Dry aniline-(from V-I)... 1,600

80 100 7 20 '1, Out 800 To crude steaming (II) l2 8 '88 '2 To glycerolextraction CHI). 1,588 '7'2 l2 1 l8 1 1,690 1,1500 sof 100 an 1,800

II. Crude steaming attracted crude {from .1). l2 8 88 2' 110 vSteam 250250 Out 5 To glycerol extraction -'(=II=I); 11 i 200 I '211 To w&te. c 1:88 52- 149 Ill. Glycerol extraction 7 Aniline solution (irom I) 1, 58872 v 12 18 =1, 690 Aniline water (from TI) 4 l'1 c 200 211 lleedwater l135 .lo glycerol concentration 1v 11 72 4 273 360 To aniline separator(V) 1,588 B 80 1,676

Tar Water Total I IV; Glycerol concentration 11.; Aqueous glycerol (fromIII). 11 72 4 273 360 Out 7 Product glycerol 72 4 18 94 Aniline water toseparator l1 196 207 Evaporated 59 59 V. Aniline separation In Fromglycerol extraction 1,588 8 80 1,676 From glycerol concentration 11 196207 Fronl aniline still (VI) 20 84 104 Out Wet aniline to still (VI)1,610 8 84 1, 702 Aniline water to recovery. 9 276 285 I VI. Anilinedehydration n Wet aniline (from V) 1,610 8 84 1, 702

Out

Distillate to separation (V) 20 84 104 Dry aniline to extractor (I) 1,590 8 1, 598

Example This example illustrates the use of a highboilingwater-insoluble heterocyclic base. 20 parts by Weight of an evaporatedextract containing 40% glycerol, 40% impurities and 20% water, areextracted with 100 parts of quinoline at a temperature between 180 and200 C. The quinoline extract is separated, cooled and treated withsufficient water to form 8.5% solution of glycerol. A single quinolineextraction removes about 25% of the glycerol in the crude liquor. 0nevaporation, the aqueous extract leaves a residue of pale yellowglycerol of high quality, having a total residue of 3.2% at 160 C.

Example 6 of my copending British application No. 8966/38,

namely it is agitated at ordinary temperature with one and a half timesits volume (about equal weight) of commercial pyridine added inportions. After thorough admixture, the mixture is allowed to separate,and the upper layer consisting of the pyridine extract is decanted. Theresidue is mixed and extracted with a second portion of pyridine, theamount used being the same as in the first extraction. The two extractsare transferred to a still arranged for indirect heating withsuperheated steam, and the liquor is distilled until the distillate isfree from water. The liquor is then decanted from impuri ties and theremainder of the pyridine distilled from it. The residue, consisting ofa crude glycerol containing about 20% total residue at 160 C. is mixedwith ten times its weight of aniline. The mixture is then mixed withsuflicient water to form a 20% solution of glycerol. The aqueousglycerol so obtained may be concentrated in the ordinary manner to givea crude glycerol having less than 5% total residue at 160 C. and capableof refinement to 98 %-99% refined glycerol grade in a singledistillation.

Instead of the aniline I could have used in the above examplesquinoline, p-toluidine, m-toluidine, o-toluidine, or a solution ofeither por o-toluidine in aniline.

Instead of separating the glycerol from the volatile nitrogen containingbase by extracting with water I could separate it by distillation.

This invention is a valuable advance in the art enabling the glycerol tobe extracted from the crude liquor in an economical manner, withoutwaste either of the product or of the organic base and to be refined to99% purity with only one distillation.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that the invention is not limited to the specific embodimentsthereof except as defined in the appended claims.

I claim:

1. A process for the recovery of glycerol from still residues whichcomprises the step of extracting the glycerol-containing liquor with asolvent selected from the group consisting of aniline, the toluidines,and quinoline, and recovering the dissolved glycerol by treating withcold Water.

2. The process for the recovery of glycerol from still residues whichcomprises evaporating a glycerol-containing liquor to a water contentbelow 30%, extracting said evaporated glycerolcontaining liquor with asolvent selected from the group consisting of aniline, the toluidinesand quinoline, and cooling and extracting the glycerol with water.

3. The process for the recovery of glycerol from still residues whichcomprises extracting the glycerol-containing liquor at a temperatureabove 100 C. with a solvent selected from the group consisting ofaniline, the toluidines, and quincline, cooling and extracting theglycerol with water.

4. The process for the recovery of glycerol from still residues whichcomprises extracting the glycerol-containing liquor with a coldwaterimmiscible primary aromatic amine.

5. The process for the recovery of glycerol from still residues, whichcomprises extracting with a volatile solvent selected from the groupconsisting of methyl and ethyl alcohol, distilling the extract to removesaid volatile solvent, and

' extracting the remaining glycerol-containing liquor with a coldwater-immiscible primary aromatic amino.

6. The process for the recovery of glycerol from still residues, whichcomprises concentrating glycerol-containing liquor derived from saidresidues to a water content below 30 and extracting the concentratedliquor with a cold water-immiscible primary aromatic amine.

7. The process for the recovery of glycerol from still residues, whichcomprises concentrating glycerol-containing liquor derived from saidresidues to a water content below 30% while extracting the concentratedliquor with a cold waterimmiscible primary aromatic amine.

ROBERT ALAN WALMESLEY.

